US2480793A - Color cinematography - Google Patents

Description

Patented Aug. 30, 1949 COLOR GIN Hans :von Fraunhofer and Harry Edward vComte, London, England No Drawin A nlication March 8., 1946, Se ial No.- 6 3 In Gre i in Au st .1 .19 5

(Cl. .88w16A) 2 Claims. 3

This inventionrelates to colour cinematography and refers particularly to the two-colour subtractive processes.

There are a considerable number of subtractive type colour cinematographic processes, most of which are two-colour methods and a number of which are three-colour systems. The two-colour methods are, at the present time, considerably simpler and more economical to produce than the three-colour types. However, it is well lgngwn in the a t of q our phe ea anhy tha two-c su t ac p ocesses a 'inc pable of reproducin the wide range of colours required order that an approximation to natural colours shall be obtained. For instance, in twa-colour subtractive processes, violets usually appear as black, purples as reddish-grey, rose as grey orange-red, while yellow is usually missing. To use a yellow dyed base for the positive film, or to dye the print yellow, in order to obtain some approximation of y ou d invo ve the sac fice i the blues and whites and the degradation of other colour proportionately.

The primary objects of the invention is the provision of simple means whereby the fidelity pf reproduction, byatwo-colour subtractive process, will be improved and in accordance with the invention we differentially process different frames in two-colour subtractive type positives, in order to give an additive effect in their projection, and thus t improve'by this simple expedient, certain colours which are not ordinarily correctly rendered in a two-colour subtractiv process.

In the specification of co-pending application No. 652,810 filed March '7, 1946, by Von Fraunhofer, one of the present inventors, has proposed to obtain an additive effect in the projection of films produced by a subtractive type process by exposing different frames of the negative through different colour filters.

The present invention proposes to gain the desired additive effect in a different way from the one suggested previously, namely by using the normal colour separations of a two-colour subtractive type integral monopack or bipack negative film, but in printing of such negative the desired additive effect is obtained by varying from frame to frame of the positive print the density of the images formed in each of the two component colours.

The preferred form of the process results in a fully exposed orange-red image in one layer of one frame being superimposed on a less exposed bluegreen image of the other layer of the same frame 2 in the one layer of the adjacent frame being superimposed on a fully exposed blue-green image of the other layer, and so on alternatingly, throughout the length of the film. A

By the introduction of this principle of printing subtractive type films, we improve the greens, yellows and other colours which often are either missing or are incorrectly reproduced as var-ia tions of greys or blacks. The reason for this improvement and considerable extension of the colour range, is that the additive effect of the changed colours resulting from the differential density of the silver deposits from frame to frame pf the one or the other of the two component subtractive colours of the two layers of the print increases, obviously, the saturation of the red values of the one frame as against the increased saturation of the blue-green image of the adjac frame a d y r su ts i e i e t t a e not .sii icient v nequ l to ca flicker i p oiectie i e e i eush censis erably extending he range i c lours e roduced bey e usua twe-eeleu s nthes s,

Among he advantag i hi n n ion are hat integr l monopack e b pack n gat ve ma ing p oc ss .ior su ract e sy he is urpe es m y be us d as a colou separation med a, and thatany double-coat d 'or wo-lay positive film .0 a y ethe typ of tw o u printin method may be utilized for printing by this principle,

It will be appreciated that this invention is susceptible of various modifications and equivalents which fall within the scope of the basic principle thereof, which is to allow a subtractive type positive print to give an additive effect in projection by suitably altering from frame to frame the density of the two component colour images.

Various methods are known for obtaining two complemental series of images, representing respectively the orange-red and blue-green colour values, by means of an integral monopack or bipack negative. Since this step in the production of the positive print does not form part of the present invention, a description of such methods is omitted as unnecessary.

Given the two elements of a bipack, one containing the orange-red colour records and the other the blue-green colour records, we proceed to print such negatives, on to the positive material chosen to suit the type of processing adopted for the purpose, in the following manner:

Assuming that the positive film represents the and vice versa, a less exposed orange-red image usual duplex material, i. e. the type carryin two following even frame is given a lesser exposure.

This lesser exposure may vary considerably de pending on the contrast of the negative or the contrast required in the positive. Thereafter, we print on to the positive the second element of the bipack. The odd frames are now given the lesser exposure while the even frames are given full exposure resulting in two layers of images in this order: The odd frames have on top a fully exposed image while on bottom only a lesser exposed image while the followin even frame has on top a lesser exposed image while on bottom it has a fully exposed image.

This variation of the respective exposures may be accomplished, as is obvious to any technician by step printing of the various frames by changing the time of exposure of each frame or increasing or decreasing the, amount of light used for the exposure. Alternatively, there may be used a suitable film loop or rotating disc containing a mask or filter for the purpose of reducing the amount of exposure given to obtain the desired variation of silver deposits from frame to frame.

The subsequent developing and processing of the so printed positive film is then carried out in the usual manner prescribed by the process to be used for this purpose.

If the positive film is to be printed from a coloured integral monopack negative film, of

which the two component series of colour images are dyed in complemental colours, we print alternate frames throughout the length of the film through a suitable filter arrangement obvious to any technician to give a fully exposed blue-green image in one layer and a lesser exposed orangered image in the other layer and We print the remaining frames through a different filter to give a lesser exposed blue-green image in the one layer and a fully exposed orange-red image in the other layer.

1. A process for the production of colour cinematographic positive film from two colour separation negatives each carrying a single series of successive images which comprises printing the first colour separation negative carrying the record only of a first colour component onto a first emulsion layer of a positive film in a manner adapted to produce an image only of said first colour component record in each frame of said first layer and to produce in the alternate frames of said layer images of higher colour density values than those produced in the adjacent intermediate images of said first emulsion layer, and printing the second colour separation negative carrying the record only of a second colour component onto a second emulsion layer of said positive film superimposed on said first emulsion layer of said positive film in a manner adapted to produce an image only of said second colour component record in each frame of said second layer in register With the corresponding image of said first colour component record in said first layer and to produce in those alternate images Which are in register with the higher density images of the first layer colour density values less than the coloLu density values produced in the adjacent intermediate images of said second emulsion layer, whereby in projection of the positive film a three colour efiect will be produced additively.

2. A process as defined in claim 1 wherein said first colour is red-orange and said second colour is blue-green.

HANS VON FRAUNHOFER. HARRY EDWARD COOTE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain June 4, 1929